The present invention relates, in general, to an improved pipe valve for use in the wind chest of a pipe organ, and more particularly to a unique control circuit and circuit board adapted for mounting on the pipe valve solenoid for convenient access, easy repair, lower current requirement, and greater reliability.
In a conventional pipe organ, the various pipes are arranged in closely spaced rows or ranks, with each pipe resting on and communicating with the interior of a wind chest. Air under constant pressure is supplied to the wind chest and flows into and through the various pipes under the control of individual pipe valves actuated by the organ keyboard. In early organs, the connection between the various keys and the individual pipe valves was essentially mechanical, with each key operating complex lever and rod arrangements to play a selected note. Although these mechanical systems were highly sophisticated and were capable of producing a surprisingly rapid response to manipulation of the keyboard, nevertheless the need for a mechanical interconnection limited the flexibility of the organ, since it was necessary to locate the keyboard console adjacent to or very close to the organ pipes.
To provide a greater degree of freedom in the location of the console, an electro-pneumatic system for controlling the flow of air to individual pipes was devised. This arrangement includes for each pipe a "chest magnet" and a corresponding leather pouch located within the wind chest. The pouch served as a diaphragm which carried the air value for the corresponding pipe, while the chest magnet controlled the flow of air to the leather pouch. The air flow to the pouch shifted the position of the valve and permitted a very rapid opening and closing of the selected pipe valve, without valve bounce. Although this system worked quite well, and in fact produced a sound which is still preferred by many listeners, nevertheless it was a complex arrangement, required a great deal of space, and was particularly susceptible to aging and drying of the leather and consequent failure of the individual valves. Organs utilizing electro-pneumatic systems of this type require periodic releathering, which is a complex, time consuming and expensive procedure.
To overcome the difficulties inherent in the electro-pneumatic valving arrangements, a direct type of electric valving was developed, wherein a solenoid is used to directly actuate a pipe valve. In this arrangement, the valve is mounted on the movable armature of the solenoid, whereby actuation of the solenoid serves to pull the valve head away from the passageway leading to the pipe, thereby providing a path for air from the wind chest into the organ pipe.
Although direct valving is simple and economical in comparison to electro-pneumatic valving, some difficulties are still experienced. In particular, the direct type of electric valving requires a high current for actuation and where the keyboard console is located some distance from the organ pipes, this high current requires the use of relatively large diameter wires leading to each magnet. This in turn results in large cables leading from the console to the wind chest. Such cables are not only hard to handle, but require a considerable amount of space, are expensive, and are unsightly. Furthermore, the large current requirements for such devices produces erosion of the keyboard contacts which control the current flow, thus producing constant maintenance problems and reducing the reliability of the direct type electric valves. An additional problem with this arrangement is the difficulty experienced by pipe organ repairmen who are familiar with the mechanical features of pipe organs, but who experience difficulty in diagnosing and repairing electrical problems, particularly where the problems involve failures of not only solenoids, but remotely located control contacts. These difficulties make repairs uncertain and their cost excessive.
In order to be able to produce smaller and more compact pipe organs, it is necessary to place organ pipes more closely together so as to conserve space, but the resultant crowding of the electrically operated valves makes the problems of reliability and repair even more acute, for closely-spaced solenoids placed side by side within an air chest are, under the best of circumstances, difficult to repair. Thus, there is a need for a reliable, compact, easy-to-repair and inexpensive direct-type electrically operated pipe valve which utilizes a relatively low control current to substantially eliminate the erosion of control contacts, will reduce the need for heavy, bulky control cables, and will provide an increased safety factor against fire hazards within the organ pipe environment.